Refrigeration apparatus



June 24, 1941. D s w 2,246,956

REFRIGERATION APPARATUS Filed July 15, 1939 INVENTOR Harold 0. Shaw.

Patented June 24, 1941 2,246,956 REFRIGERATION APPARATUS Harold D. Shaw,

Longmeadow, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 15, 1939, Serial No. 284,634

Claims.

This invention relates to mechanical refrigerating apparatus and more especially to a control for such apparatus.

One object of the invention is to provide a control which tends to maintain the interior of a refrigerator at a substantially constant temperature regardless of the temperature exterior of the refrigerator.

A further object is to provide a compensated control apparatus which is readily installed in a refrigerator of conventional design. I

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. l is a schematic drawing of a mechanical refrigerator embodying the control apparatus of this invention; and,

Fig. 2 is a detailed view of a portion of the control apparatus.

Referring especially to the drawing for a detailed description of the invention, the reference numeral 10 designates a cabinet of a refrigerator having insulated walls ll forming a food storage compartment l2. An evaporator I3 is secured in the upper portion of the cabinet ID for cooling the same and is provided with an entrance tube l4 of relatively low heat storage capacity. The evaporator I3 is supplied with liquid refrigerant through a capillary flow impedingtube I6, which conducts the refrigerant from a condenser H to the entrance tube I4 of the evaporator I3. The vaporized refrigerant is withdrawn from the evaporator l3 through a suction tube l8 bya compressor l9 which forces the compressed refrigerant vapor through a conduit 2| into the condenser II. A fan 22 draws air through the condenser I! to cool the same. The fan 22 is driven by-a motor 23 and the compressor I9 is driven by'a second motor 24. The motor 24 receives electrical energy through leads 26 from a supply line 21.

A switch embodying a fixed.contact element 28 and a movable contact element 29 is placed in one of the leads 26 in series with the motor 24. The contact elements 29, 29 are opened and closed by a snap-acting control device comprising a lever 3|, a second lever 32, and a spring 39,

forming an overcenter linkage. The lever 3| is actuated by 'an expansible bellows 25. As thus far described, the apparatus is old and wellknown in the art.

According to the invention, the bellows 25 communicates with a vessel 33 comprising a tube 33 and abulb 34 containing a small quantity of a volatile liquid 35. The bulb 34 is exposed to the air in the food compartment l2 or to any material in the food compartment l2, the temperature of which material is intended to be held relatively constant. A portion 36 of the tube 33 is placed in heat exchange relationship with the entrance tube l4 of the evaporator l3 through a strip of metal 31. A heater 39 and a thermostatic switch 26 for controlling the same are located adjacent the portion 36 of the tube 33, andthe heater 39, the switch 20, and the portion 36 are preferably enclosed in an insulated housing- 38.

The thermostatic switch 20 comprises a bimetallic blade 42, a contact element 40 thereon, and a second fixed contact element 45. The heater 39 and the thermostatic switch 20 are connected in series in a circuit comprising leads 4| connected, respectively, to the contact elements 28, 29 so that the heater is in series with the motor 24 when the contact elements 28, 29 are open and the contact elements 40, are closed. When the contact elements 28, 29 are closed, the heater is short-circuited.

When the heater '39 is energized, it heats andmaintains the portion 36 of the tube 33 at a tem-' perature somewhat higher than the temperature at which the bulb 34 is maintained when the refrigeratoris in operation.

The operation of the control device is as follows: Assume that the food chamber l2 has been cooled to its normal temperature, and that-the contact elements 28, 29 and 46, 45 are in the open position and the volatile liquid 35 is in the bulb 34 as shown'in Figs. 1 and 2. In this position, the refrigerant-supplying apparatus, including the motor 24 and the compressor I6, is not operating and the heater 39 is not energized. Heat will gradually leak through the walls H of the cabinet III and warm the food chamber I2 in which the bulb 34 is located. As the temperature of the bulb 34 increases, the volatile liquid 35 therein vaporizes and expands the bellows 25 to close the contact elements 28, 29. The closing of the contact elements 28, 29 starts the motor 24 and initiates the supply of refrigerant to entrance tube l4 and the evaporator l3.

The vaporizing refrigerant in the tube l4 gradually cools the metal strip 31 and the portion 36 of the conduit 33 to a temperature below that of the bulb 34. The liquid 35in the bulb 34, being warmer than the portion 36, will vaporize and condense in the portion 36 and adhere to this portion by capillary attraction. The vapor pressure of the liquid, therefore, will no longer conform to the temperature of the bulb 34 but will conform to the lower temperature of the portion 36 of the tube 33. This decrease in temperature reduces the vapor pressure of the liquid, and the expansible bellows 25 will contract and open the contact elements 28, 29 thereby stopping the flow of refrigerant to the evaporator l3.

Generally before the contact elements 28, 29 have opened, the contact elements 40, 45 are closed by the bi-metallic blade 42 in response to the lower temperature prevailing in the insulated housing 38 and brought about by the heat withdrawn from the interior of the housing 38 'by the metal strip 31 and the refrigerant in the tube l4. When the contact elements 49, 45 are closed under the action of the bi-metallic blade 42, and contact elements 28, 29 are opened by the decreased pressure of the liquid 35, the heater 3 is energized and quickly warms the tube portion 35 above the temperature of the bulb 34; however, in a capillary tube system, as shown, the warming time should be of sufficient duration to permit the pressure between the high and low pressure sides of the system to equalize so themotor 24 will start. The warming of the tube portion 36 vaporizes the liquid 35 therein and condenses it in the bulb 34 since the latter is now the coldest portion of the vessel 30. The bulb 34, therefore, again assumes control and will close the main contact elements 28, 29 when the temperature of the bulb 34 increases because of heat leakage through the walls I l of the cabinet or other causes. The metal strip 31 is secured to the tube l4 in preference to the evaporator l3 because the former has a smaller heat storage capacity so that less heatis required in the heater 39 to raise the tube section 36 to the required temperature. It is also preferably connected above the normal level of the liquid refrigerant in the tube l4 where the heat storage capacity is smaller.

It will be apparent from the above that this embodiment of the invention provides a control for a mechanical refrigerator which is responsive to the temperature of the air in the refrigerator for starting the refrigerating cycle and which thereby maintains the air in the refrigerator at a substantially constant temperature. The control apparatus of this invention is also adapted for installation in refrigerators of conventional design because all the mechanical changes required are to install the control elements illustrated in Fig. 2, and to pass the wires 32 through the walls of the refrigerator to the contact elements 28, 29. In those cases where the contact elements 28, 29 are within the refrigerated cabinet I 0, the passing of the wires 4| through the walls of the refrigerator is not necessary.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes'and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, means responsive to the vapor pressure of' said fluid for starting and stopping the flow of refrigerant from the refrigerant-supplying means to the cooling unit, and means for heating the second portion of the vessel substantially solely during the period between the stopping and the starting of the flow of refrigerant to the cooling unit to maintain the temperature of the second portion of said vessel above that of the first portion thereof during said period.

2. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, said cooling unit having a portion of low heat storage capacity, means for supplying refrigerantto said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion in heat exchange relationship primarily with the portion of the cooling unit of small heat storage capacity, a volatile fluid in said vessel, said fluid being partially in the liquid phase, means responsive to the vapor pressure of said fluid for starting and stopping the flow of refrigerant from the refrigerantsupplying means to the cooling unit, and means for heating the second portion of the vessel substantially solely during. the period between the stopping and the starting of the flow of refrigerant to the cooling unit to maintain the temperature of the second portion of said vessel above that of the first portion thereof during said period.

3. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the, media in said cabinet'and a second portion in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, means responsive to the vapor pressure of said fluid for starting and stopping the flow of refrigerant from the refrigerant-supplying means to the cooling unit, and means for heating the second portion of the vessel by a heat source independent of the ambient air and of said refrigerant-supplying means.

4. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, said cooling unit having a portion of low heat storage capacity, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion in heat exchange relationship primarily with the portion of the cooling unit of small heat storage capacity, a volatile fluid in said vessel, said fluid being partially in the liquid phase, means responsive to the vapor pressure of said fluid for starting and stopping the flow of refrigerant from the refrigerantsupplying means to the cooling unit, and means for heating the second'portion of the vessel by a heat source independent of the ambient air and of said refrigerant-supplying means.

5. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, a switch responsive to the vapor pressure of said fluid for starting and stopping the flow of refrigerant from the refrigerant-supplying means to the cooling unit, and means responsive to said switch for heating the second portion of the vessel during the period between the stopping and the starting of the flow of refrigerant to the cooling unit to maintain the temperature of said second portion above that of the first portion thereof during said period. t k

6. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit therefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, a switch comprising two contact elements responsive to the vapor pressure of said fluid for starting and stopping the flow of refrigerant from the refrigerant-supplying means to the coolingunit, and

an electric heater in heat exchange relationship with said second portion and connected across said contact elements for heating the second portion of the vessel during the period between.

the starting and the stopping of the flow of refrigerant to the cooling unit to maintain the temperature of the second portion of said vessel above that of the first portion thereof during said period.

'7. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unittherefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having-a first portion thereof in heat exchange relationship primarily with the media in said cabinet and a second portion'in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, a switch comprising two contact elements responsive to the vapor pressure of said fluid forstarting and stopping the flow of refrigerant from the refrigerant-supplying means to the cooling unit, an electric heater in heat exchange relationship with said second portion and connectedracross said contact elements for heating the'second above that of the first portion thereof during said period, and a thermostat associated with said heater for limiting the temperature thereof.

I 8. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling 'unit therefor, means driven by an electric motor for supplying refrigerant to said cooling unit, a controlling device for said motor comprising a vessel having a first portion thereof in heat exchange relationship primarily with the media in said cabinet, and a second portion in heat exchange relationship primarily with the cooling unit, a volatile fluid in said vessel, said fluid being partially in the liquid phase, a switch responsive to the vapor pressure of said fluid forstarting and stopping said motor, an'electric heater in heat exchange relationship with said second portion o and connected across said switch for heating the second portion of the vessel during 'the period that the switch is open to heat the second portion of said vessel to a temperature above that of the first portion thereof.

9. In a mechanical refrigerator; the combination of an insulated cabinet, a cooling unit therefor, means for supplying refrigerant to said cooling unit, and a controlling device for said means comprising a vessel having a first portion thereof in heat exchange relationship primarily with ond portion of the vessel substantially solely dur-v ing the period between the stopping andthe starting of the flow of refrigerant to the cooling unit to maintain the temperature of the second portion of'said vessel above that of the first portion thereof during said period.

10. In a mechanical refrigerator, the combination of an insulated cabinet, a cooling unit portion of the vessel during the period between the starting and the stopping of the flow of refrigerant to the cooling unit to maintain the temperature of the second portion of said vessel therefor, meansfor supplying refrigerant to said cooling unit, and acontrolling device for said means comprising a vessel having a first portion thereofin heat exchange relationship primarily with the media in saidcabinet and a second portion in limited heat exchange relationship primarily with the cooling unit, a volatile. fluid in said vessel, said fluid being partially inthe liquid phase, means responsive to the vapor pressure of. said fluid for starting and stopping the flow of refrigerant from the refrigerant-supplying means to the cooling unit. and means for heating the second portion of the vessel. by a heat sourceindependent of the ambient air and of said refrigerant-supplying means.

[HAROLD p. SHAW. 

